In wireless communication systems including third generation protocol partnership (3GPP) and long term evolution (LTE) systems, random access resources are available for uplink communication. In general, 64 signatures or resources can be made available in a non-synchronized random access resource. These signatures can always be available per access resource. In addition, multiple random access resources may be defined within one access period in order to provide sufficient number of random access opportunities. Thus, the available number of signatures in a cell at a particular time may be larger than 64.
It has been proposed to allocate some of these signatures within the random access resource to be reserved for dedicated uses. These uses include handover where the dedicated signatures are allocated by a base station or node B to minimize latency and avoid contention. If at the time of handover timing information is not available to the user equipment, it uses the contention-free access using the dedicated signatures and dedicated resources. Dedicated signatures and resources can also be used to maintain or recover uplink synchronization. In this example, the dedicated resources can be used to provide timing information whereby signatures are provided at a specific time. As a result there is no contention in the signature transmission and the node B can identify each user equipment by the timing and signature used.
In another case, dedicated signatures or resources can be used in user detention procedures where users that are interested in upcoming E-MBMS service transmit their response using a common signature. In this case, a dedicated signature is allocated to specific MBMS service and the node B receives an indication whether any user equipment in the cell is interested in this service. In addition, for user equipment that is an idle mode, NACK feedback can be provided using one signature for the feedback. Responses from multiple user equipment can be transmitting using the common dedicated signature. Moreover, rescheduling requests can be transmitted in a contention-free manner by reserving a subset of signature sequences for scheduling request purposes. Thus, each user equipment is assigned a reserved sequence at a specific time to be used as a scheduling request indicator.
As can be seen from the above description, there are multiple uses for dedicated signatures and resources within the random access resource. In addition, each of the uses can vie for the same dedicated resources at the same time. As can be appreciated, the competing uses for the dedicated resource can cause those resources to be blocked for some users. Therefore there is a need to overcome blocking of the dedicated resources to users that may be blocked. In addition, there is a need to keep the complexity of allocated resources and signatures within the random access resource low. This is to be balanced with the need to provide fast responses for requested resources. As is evident, it has been proposed to have dedicated signatures for dedicated uses. This, however, reduces the availability of these dedicated signatures for other purposes. In sum, there is a need for allocation of dedicated and non-dedicated signatures and resources at the highest utilization possible to reduce blocking.
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